Biochemical and behavioral studies conducted over the past year on audiogenic seizures in inbred strains of mice have provided the information that impairment of NA transmission may be of considerable importance to elaboration of sound-induced seizures related to ontogeny. Also of apparent importance to seizure production is altered serotonin transmission at the age of maximal seizure response. In the coming year, radiolabelled tyrosine and tryptophan will be utilized to label the monoamine neurons in the brain and the effect of the sound stimulus on the synthesis, release, and metabolism of the monoamines will be investigated. Using this method, changes in transmission in various regions can be identified as a function of age and strain. Additionally, a drug with a catecholamine-like structure has been found to elicit sound-induced seizures in genetically insensitive strains of mice and laboratory rats. The elicited seizures have many characteristics similar to the seizures elicited in genetically sensitive animals. The biochemical responses in the brain following administration of the seizure inducing drug will be investigated.